Tanning with alkylbenzene sulfonate in combination with chrome tanning



TANNING WITH ALKYLBENZENE SULFONATE 1N CGMBINATION WITH CHROME TANNINGFriedrich Schmitt, deceased, late of Dusseldorf, Germany, by AliceSchmitt, geb. Neukirchner, heir, Dusseldorf, Germany, assiguor to BoehmeFettchemie G.m.b.H., Dusseldorf, Germany No Drawing. Filed Dec. 5, 1956,Ser. No. 626,547 Claims priority, application Germany June 21, 1951 2Claims. (Cl. 8-94.33)

' mal collagen fiber and can be smoothly Worked into the skins. They maybe combined with the ordinary mineral, vegetable, or synthetic tanningagents or with tanning agents used in oil tanning.

The hydrocarbon radicals introduced into the sulfonic acids determine toa certain extent the properties and efiect of the sulfonic acids. Withan increasing chain length of the aliphatic hydrocarbon radicals,preferably from 12 to 18 carbon atoms, the tanning agent will assume thecharacter of a tanning agent used in oil tanning or the character maybecome more pronounced in that respect. By using the tanning agentsaccording to the present invention, the tanning process may be carriedout much more rapidly than with the use of the conventional agents foroil tanning, such as fish oils.

The tanning agents according to the invention may be used for tanninghides and furs of all types, more particularly hides of calves, sheep,goat, deer, does, or cows. The hides are treated by known methods bysoaking in Water, liming, and/or pickling, if necessary.

The salts of sulfonic acids substituted by higher molecular hydrocarbonradicals to be used for the tanning method according to the inventionare for instance as follows: alkylsulfonic acids, alkylarylsulfonicacids, alkylcycloalkylsulfonic acids, and the like. The aliphatichydrocarbon radicals can be branched or straight .and may contain 12-18carbon atoms or more. The

sulfonic acids may, furthermore, contain in the hydrocarbon radicalsheteroatoms or heteroatom groups, or substituents; as such are namedmore particularly carbonarnide or sulfonamide groups; as heteroatoms,sulphur and oxygen. As substituents, are mentioned oxy groups. Thesulfonic acids may also contain several sulfonic acid radicals.

The following examples are given for sulfonic acids to be used accordingto the invention: Alkylcyclohexylsulfonic acids (alkyl radicals about CC naphthenylsulfonic acids, alkylbenzenesulfonic acids, or mixtures ofthe same (alkyl radicals about C C higher moleculara1kylnaphthalenemonosulfonic acids or their mixtures, acyloxy, oracylaminoalkanesulfonic acids, and the like.

The sulfonic acids are used in the form of their Watersolnble salts withinorganic or organic bases, for instance in the form of their alkalimetal or ammonium salts or in form of their organic amino compounds,

In operation, they are kneaded into the hides, either 2,973,240 PatentedFeb. 28, 1961 directly or in the form of their aqueous solutions oremulsions in as high a concentration as feasible; as to the amount oftanning agents used, it should be about 5 to 8% with reference to theweight of the hides. After or before the agents have been worked intothe hides, the leather is processed and finished according toconventional methods. In the combination process which is used, thesalts of the sulfonic acids used according to the invention may beapplied in a step by themselves before or after treatment of the hideswith the known tanning agents.

As mentioned before, the tanning agents may be used in oil tanning andmay, in that case, be combined with fish oils or sulfonates of aliphaticalcohols.

The invention will now be illustrated by a number of examples, but itshould be understood that these are given by Way of illustration and notof limitation, and that many modifications of the amounts and substancesmentioned can be made without departing from the spirit of theinvention.

In the following examples the percentage of tanning agents given refersto the weight of the hides.

Example 1 a solution containing of water, 0.5 alkylbenzene sodiumsulfonate (alkyl radicals C -C 1 to 2% formic acid, and 6 to 8% sodiumchloride. After the pickling operation the hides should have a pH-valueof 3.2 to 3.8 in the cut surface.

After having been allowed to drip, the hides are kneaded for 4 hours ata temperature of about 20 C. with a 5% solution of alkylbenzenesulfonate(alkyl radicals C C which has been diluted with the double or tripleamount of water. Subsequently, the hides are treated with 0.3-0.7%chromium oxide in form of a concentrated solution of a commercialchromium salt in alkaline solution adjusted to 4:126:12. The tanningtreatment is terminated after 2 hours and the leather is allowed toremain lying covered on the block for 4 to 5 days. Subsequently, rinsingwith lukewarm water takes place for 15 to 20 minutes and finishingtreatment is effected in the known manner. The leather is full and softto the touch and has high resistance to tear. The grain is smooth andclosed.

Example 2 Well unlimed and pickled split cowhides are pretanned with 1to 1.5% formaldehyde, sodium bicarbonate being added in half the amountof the added formaldehyde. The split hides remain overnight on theblock, whereafter they are sammied and pared. Then, an emulsionconsisting of 5-6% alkylbenzene sodium sulfonate (alkyl radicals C -C 6%of fish oil (iodine No. over and 0.5% of formic acid or 1.5% of amixture of low molecular fatty acids obtained in the oxidation ofparafiin, are kneaded in a conventional kneading vat or a hot air vatfor 3-4 hours.

The leather remains overnight on the block and is then hung up for 3-4days in a warm room, whereafter it is kept for 14 days in a pile. Theleather may also be immediately put in a pile, similar to the tanning ofsuede leather, and may be subsequently dried. Thereafter, the leather iswashed with calcined soda in an amount of 0.3 to 0.5 in order to removeexcess of fish oil, Whereupon it is dried and finished as usual.

The split leather has a suede-like character and is distinguished by avery high tear resistance. As compared to chromium tanned split leather,it has a much better heat-insulating property.

Example 3 Split cowhides which have preferably been ashed, unlimed andpickled, are pre-tanned with 0.5 to 1.5% of formaldehyde, which in aconventional manner has been de-acidified with sodium bicarbonate. Thehides remain overnight in the de-acidified formaldehyde, then they areallowed to drip on the block and are sammied and pared.

Thereupon, a. mixture consisting of 2 to 3% alkylbenzene sodiumsulfonate (alkyl radicals C12C18) with 23% alkyl sodium or ammoniumsulfonate (alkyl radicals C -C and 6% of fish oil (iodine No. over 140)is worked into the leather in a tanning vat at 20-30 C. The operationtakes 3-4 hours. Instead of saturated alkyl sulfonates, unsaturated onesmay also be used.

The hides remain overnight on the block and are then hung up in a warmroom. They are thereafter allowed to age for some time on bark. Thesplit leather may be piled up for a few days before drying. Afterdrying, the leather is washed with 03-05% calcined soda, in a mannerused in suede tanning.

Example 4 Cowhides pickled as usual are kneaded for 4-5 hours with anemulsion of 6% fish oil (iodine N0. over 140), 4% alkylbenzene sodiumsulfonate (alkyl radicals C C and then treated as in Example 2. Leatherobtained is distinguished by a specially supple touch, high tearresistance and a smooth, adherent grain.

Example Pickled cowhides having a pH-value of 3.2 to 3.6 are kneaded ina tanning vat for 3-4 hours at a temperature between 20 and 30 C. with2% alkylbenzene sodium su1 fonate (alkyl radicals C C 2% alkyl sodiumsulfate (alkyl radicals C C especially also the oleyl radical) and with2% alkyl sodium sulfonate (obtained by treatment of an aliphatichydrocarbon fraction C -C with sulfur dioxide and chlorine, andsubsequent saponification with caustic soda) with addition of 5% fishoil (iodine No. over 140).

Further treatment as in Example 2. The single components as well as themixture of oil-tanning agents are rapidly taken up by the hides.

As compared to chromium tanned leather, the leather has a softer, moreflexible touch. It has a very high tear resistance and is well permeable-to air without increase in moisture absorption.

Example 6 Pickled doe hides are treated in a mixture of water, 0.5%alkylnaphthalene sodium sulfonate (alkyl radicals C 43 1-2% formic acidand 2-4% of an aqueous organic acid mixture obtained in the paratfinoxidation and 610% sodium chloride, the whole being adjusted to apH-value of 3.5. After dripping, the hides are kneaded for 4 hours with6% alkylnaphthalene sodium sulfonate (alkyl radicals C -C diluted withthe same or double amount of water. Subsequently, I treat with a weakcommercial chromium salt 0.30.7% by weight in alkaline solution adjustedto 4:12-6:12. Subsequent treatment and finishing operations areconventional. Leather so obtained is soft and Warm to the touch and isparticularly suitable for the manufacture of gloves, wearing apparel andleather pants.

What is claimed is:

1. A method of tanning unhaired, pickled animal skins having a pH ofapproximately 3.2 to 3.8 comprising kneading said skins with a 5 percentaqueous solution of an alkylbenzene sulfonate having from 12 to 18carbon atoms in its alkyl radical for 3 to 4 hours at 20 to 30 C. and inthe presence of water in an amount of approximately 2 to 3 times thevolume of said solution, thereafter tanning the leather thus obtainedfrom said skins with an alkaline, water-soluble chromium salt tanningsolution containing approximately 4 to 6 parts of said salt in 12 partsof water, and washing said leather to obtain a full soft surface havinghigh tear resistance.

2. Amethod as claimed in claim 1 wherein said skin is kneaded with fishoil after pickling and before kneading with said sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS1,715,410 Daimier et al. June 4, 1929 1,927,910 Balle Sept. 26, 19332,249,757 Flett July 22, 1941 2,692,180 Schmitt et al. Oct. 19, 1954

1. A METHOD OF TANNING UNHAIRED, PICKLED ANIMAL SKINS HAVING A PH OFAPPROXIMATELY 3.2 TO 3.8 COMPRISING KNEADING SAID SKINS WITH A 5 PERCENTAQUEOUS SOLUTION OF AN ALKYLBENZENE SULFONATE HAVING FROM 12 TO 18CARBON ATOMS IN ITS ALKYL RADICAL FOR 3 TO 4 HOURS AT 20 TO 30*C. AND INTHE PRESENCE OF WATER IN AN AMOUNT OF APPROXIMATELY 2 TO 3 TIMES THEVOLUME OF SAID SOLUTION, THEREAFTER TANNING THE LEATHER THUS OBTAINEDFROM SAID SKINS WITH AN ALKALINE WATER-SOLUBLE CHROMIUM SALT TANNINGSOLUTION CONTAINING APPROXIMATELY 4 TO 6 PARTS OF SAID SALT IN 12 PARTSOF WATER, AND WASHING SAID LEATHER TO OBTAIN A FULL SOFT SURFACE HAVINGHIGH TEAR RESISTANCE.